The present disclosure herein relates to a communication system, and more particularly, to phase signal generating apparatuses, which can control a phase.
Generally, in a communication system, phase imbalance deteriorates the performance of a transmitter-receiver.
The transmitter-receiver uses an in-phase (I) signal and a quadrature phase (Q) signal for transmitting/receiving a signal. The in-phase signal and the quadrature phase signal have a 90-degree phase difference therebetween.
The transmitter-receiver generates an in-phase signal and a quadrature phase signal through an oscillator. The transmitter-receiver mixes the in-phase signal and the quadrature phase signal with a transmission signal through a mixer. The transmitter-receiver also mixes the in-phase signal and the quadrature phase signal with a reception signal through a mixer. In this way, the transmitter-receiver up-converts the transmission signal or down-converts the reception signal with the in-phase signal and the quadrature phase signal for transmitting/receiving a signal.
Phase imbalance is caused by a sum of a phase imbalance of the oscillator and a phase imbalance of the mixer. Because an in-phase signal and a quadrature phase signal that are generated in the oscillator do not have a 90-degree phase deviation. By symmetrically designing an in-phase signal mixer and a quadrature phase signal mixer, phase imbalance can be reduced. However, phase imbalance is inevitably caused by parasitic components that are generated when actually fabricating the mixer. This phase imbalance decreases a Signal to Noise Ratio (SNR) and thus increases a Bit Error Rate (BER), thereby degrading the performance of a transmitter-receiver.